The yellow phosphorus production process by electric furnace in industry application is divided into the production process using phosphorus furnace with a large self baking electrode and the production process using phosphorus furnace with multiple electrodes. The two processes are different in terms of type and scale of the electric furnace, treatment requirements for the raw material fed into the furnace, and dust collection measures, but basically the same in respect to the main flow, i.e., delivering mixture proportioned by phosphate ore, silica and coke into an electric furnace, generating furnace gas by the reduction reaction of the mixture in the electric furnace, making furnace gas escape from the molten zone of reaction, discharging furnace gas with particle impurities of the mixture from the electric furnace after passing through the furnace gas filter layer formed by the continuously supplemented mixture in the upper part of the furnace, then obtaining yellow phosphorus product through dust removal, condensation and scrubbing, refining and separation process, and finally recovering or discharging tail gas.
Wherein, when the capacity of transformer of the electric furnace is generally 50,000-90,000 KVA, the output is generally more than 30,000 tons/yr., the self baking electric furnace is adopted. In the production process using phosphorus furnace with a large self baking electrode, the requirements are very stringent for raw materials fed into the furnace (e.g., moisture and particle size of coke fed into the furnace), lump ore cannot be directly fed into the furnace without pretreatment with sintering process and pelletization process, and the temperature of the generated furnace gas is generally higher than 350° C.; the furnace gas discharged from the electric furnace enters an electrostatic dust collector (i.e., dry dust removal), the dedusted and purified furnace gas (the dust content is generally about 50 mg/m3) enters a condensation and recovery system to obtain crude phosphorous, and the crude phosphorous is refined in a crude phosphorous refining system to obtain yellow phosphorous product.
The capacity of the transformer and the output of the electric furnace in the production process using phosphorus furnace with multiple electrodes are much less than those in the process using phosphorus furnace with a large self baking electrode. When the capacity is generally less than 28,000 KVA and the output is 7,000-10,000 tons/yr., molding graphite electrode is adopted, and 6 or 7 three-phase graphite electrodes with a diameter of 500 mm or 600 mm are arranged; sintered material or pellet material is not required for raw material fed into the furnace. With drying pretreatment adopted, the lump ore is fed into the furnace and the furnace gas temperature is generally 100-170° C.; furnace gas discharged from the electric furnace is directly fed into the condensation and recovery system (i.e., wet dust removal), the condensed yellow phosphorus is turned into crude phosphorus after entering the collecting tank, and then the crude phosphorus is refined in the crude phosphorus refining system to obtain the yellow phosphorus product and much phosphorus sludge.
The above-mentioned production process using phosphorus furnace with a large self baking electrode can produce less phosphorus sludge and wastewater, but it has such disadvantages as large construction expenses for supporting facilities of the electrostatic dust collector, high operation and maintenance costs, high personnel technical requirements, and insufficiently treated dust in furnace gas resulting in exhaust problem of PM2.5 in the tail gas. Meanwhile, the production process using phosphorus furnace with multiple electrodes will produce much phosphorus sludge which is difficult to separate, and the dust content in tail gas is higher.
The applicant applying for the invention patent has provided one method and an apparatus using phosphorus furnace with multiple electrodes for yellow phosphorus production and the other method using phosphorus furnace with a large self baking electrode for yellow phosphorus production respectively in application documents No. 2013104546439 and No. 2013104548326 of Chinese patents. Since a dry dust removal system is used for dust removal and purification of electric furnace phosphorus-producing furnace gas in the two methods, and a filter provided with a porous membrane element is used for fine filtration of electric furnace phosphorus-producing furnace gas at high temperature in the dry dust removal system, very little phosphorus sludge is produced during the phosphorous production process by the two methods, and the dust content of tail gas can be reduced. However, because a spray cooling process is still adopted when the dedusted and purified furnace gas is condensed via the two methods, a certain amount of phosphorus sludge may be produced and a large amount of cooling water will be consumed, and a large amount of wastewater will be generated subsequently, resulting in the increased steam consumption during refining of crude phosphorus and the wastewater treatment problem. So far the yellow phosphorus production by electric furnace process is to produce crude phosphorus by the spray cooling process which has been written into the yellow phosphorus production specification.